It seems to me that this was recently posted about on this site. 
#!/usr/bin/perl
use strict;

my $find = "r";
my $replace = "X";

my $input = "superfrink";

my $tmp = reverse $input;
$tmp =~ s/$find/$replace/;
my $output = reverse $tmp;

print "input: $input \n";
print "output: $output \n";

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Update: Here is the sample output.
frink@scanbox:~ $ ./397370.pl 
input: superfrink 
output: superfXink 
frink@scanbox:~ $

[download]

In reply to Re^2: Replace the last letter by superfrink
in thread Replace the last letter by Anonymous Monk

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